Effects of Cadmium Stress on Carbon Sequestration and Oxygen Release Characteristics in A Landscaping Hyperaccumulator—Lonicera japonica Thunb.

Abstract

The carbon sequestration and oxygen release of landscape plants are dominant ecological service functions, which can play an important role in reducing greenhouse gases, improving the urban heat island effect and achieving carbon peaking and carbon neutrality. In the present study, we are choosing Lonicera japonica Thunb. as a model plant to show the effects of Cd stress on growth, photosynthesis, carbon sequestration and oxygen release characteristics. Under 5 mg kg−1 of Cd treatment, the dry weight of roots and shoots biomass and the net photosynthetic rate (PN) in L. japonica had a significant increase, and with the increase in Cd treatment concentration, the dry weight of roots and shoots biomass and PN in the plant began to decrease. When the Cd treatment concentration was up to 125 mg kg−1, the dry weight of root and shoots biomass and PN in the plant decreased by 5.29%, 1.94% and 2.06%, and they had no significant decrease compared with the control, indicating that the plant still had a good ability for growth and photoenergy utilization even under high concentrations of Cd stress. The carbon sequestration and oxygen release functions in terms of diurnal assimilation amounts (P), carbon sequestration per unit leaf area (WCO2), oxygen release per unit leaf area (WO2), carbon sequestration per unit land area (PCO2) and oxygen release per unit land area (PO2) in L. japonica had a similar change trend with the photosynthesis responses under different concentrations of Cd treatments, which indicated that L. japonica as a landscaping Cd-hyperaccumulator, has a good ability for carbon sequestration and oxygen release even under high concentrations of Cd stress. The present study will provide a useful guideline for effectively developing the ecological service functions of landscaping hyperaccumulators under urban Cd-contaminated environment.